research article influence of the weight of a school...

Research ArticleInfluence of the Weight of a School Backpack on SpinalCurvature in the Sagittal Plane of Seven-Year-Old Children

Katarzyna Walicka-CupryV,1 Renata Skalska-Izdebska,1

Maciej RachwaB,1 and Aleksandra TruszczyNska2

1Department of Medicine, Institute of Physiotherapy, University of Rzeszow, Warszawska 26A Street, 35-205 Rzeszow, Poland2Physiotherapy Department, Jozef Piłsudski University of Physical Education, Marymoncka 34, 00-968 Warsaw, Poland

Correspondence should be addressed to Katarzyna Walicka-Cuprys; [email protected]

Received 24 April 2015; Revised 22 July 2015; Accepted 18 August 2015

Academic Editor: Frederic Noe

Copyright © 2015 Katarzyna Walicka-Cuprys et al. This is an open access article distributed under the Creative CommonsAttribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work isproperly cited.

The aim of the paper was to determine a correlation between the weight of a child’s backpack, their body weight, and certain featuresof their body posture. Material and Methods. The study group consisted of 109 children, all aged seven years. The parameters ofbody posture were determined using the Zebris Ultrasonic System. Results. The number of children carrying a school backpackin accordance with recommendations was 44 subjects (40.37%). Statistically significant changes were found in the total length ofthe spine (𝑍 = 2.223, 𝑝 = 0.026) and between backpack weight and changes in the following parameters: the total length of thespine (𝑟

𝑠= −0.3999, 𝑝 = 0.017), the length and the angle of the lumbar lordosis (𝑟

𝑠= −0.3352, 𝑝 = 0.049), the angle of the lumbar

lordosis (𝑟𝑠= −0.5065, 𝑝 = 0.002), and the sacral angle (𝑟

𝑠= −0.4279, 𝑝 = 0.010). Conclusions. Wearing a backpack heavier than

10% of one’s body weight can cause shallowing of the lumbar lordosis and a tendency towards a vertical position of the sacrum.Monitoring the weight of children’s school backpacks and enabling them to leave books and notebooks at school would probablybe beneficial in reducing the daily burden put on children’s spines.

1. Introduction

Theproblemof bad posture in children and adolescents is stilla current issue, frequently addressed in scientific publications[1–4]. During the early school period (seven to 10 years), bodygrowth is relatively stable [5]. Kyphotic and balanced bodypostures dominate during the period of seven to eight yearsof age [6]. However, when the child begins to attend school,their time spent in a sitting position is extended, which canresult in disorders of posturogenesis. Hence, this period iscalled “the first critical period of posturogenesis.”

Children at this age are exposed to a number of factorsthat predispose them to the occurrence of bad posture.One ofthese factors is carrying a backpack that is too heavy for them.According to the literature, this problem affects between 40%and 70% of children in developed countries [5, 7]. Excessivebackpack load causes back pain and spinal deformities inchildren [8–10].The pain associatedwith carrying a backpack

is referred to as “backpack syndrome.” This syndromeincludes the following factors: abnormal body posture caus-ing headaches, fatigue, and cervical and lumbar pain [11, 12].

Recommendations concerning the weight of school back-packs in relation to body weight diverge depending on theorganization. In 2009, the American Occupational TherapyAssociation (AOTA) and the American Physical TherapyAssociation (APTA) recommended not carrying a backpackheavier than 15% (or between 10% and 20%) of the student’sbody weight; in 2012, this was changed to 10% of their bodyweight [13]. The American Chiropractic Association (ACA)recommended that backpack weight should not exceed 5–10% of the child’s body weight. There are dangers thatexcessive loads pose to thematuring spine [14]. Many authorshave concluded that the weight of a school backpack shouldnot exceed 10% of the child’s body weight [15], based on thefact that it can affect their spinal posture, foot shape, and gait[16–19]. However, there is still no clear information about

Hindawi Publishing CorporationBioMed Research InternationalVolume 2015, Article ID 817913, 6 pageshttp://dx.doi.org/10.1155/2015/817913

2 BioMed Research International

Table 1: Basic biometric parameters characterizing the study group(𝑁 = 109).

Mean Range SDBody weight (kg) 25.55 19.02–38.00 4.7Body height (m) 1.25 1.13–1.39 0.1SD: standard deviation.

the impact that a school backpack has on the formation ofspinal curvature in the sagittal plane in school children.

Theweight of backpacks carried as part of everyday activ-ity may be related to the shape of curvatures of the spine, inparticular when the activity requires taking a specific, forcedposture. A child carrying a heavy backpack will tend to leanforward to balance their centre of gravity, which results in areduction of lumbar lordosis and increased thoracic kyphosis[4]. Such a posture may become habitual and be maintainedeven after taking the backpack off. Thus, the authors of thisstudy decided to look more closely into this issue.

The following hypotheses were set up: does the weight ofthe backpack constitute the recommended 10% of the bodyweight of a seven-year-old child? Does curvature of the spinechange in children who carry a backpack heavier than 10% oftheir body weight?

The aim of the paper was to describe the relationshipbetween the load of a child’s school backpack and the occur-rence of changes in the parameters of their body posture inthe sagittal plane.

2. Material and Methods

Thestudywas conducted at the end of the first year of primaryschool atWincenty Pol Primary School in Lesko, Poland.Thestudy group included 109 children, all aged seven years: 58girls and 51 boys. The children had not attended a receptionclass before. The children in the study group were carryingtheir backpacks on their way to school and back and goingfrom one classroom to another during breaks, for an averagetotal time of 50minutes a day.The anthropometric data of thechildren are summarized in Table 1.

The studywas conducted after obtaining consent from theschool principal, parents, and the subjects themselves and aspart of a larger research project which had been approvedby the local Bioethics Committee at the Faculty of Medicine,University of Rzeszow.

Inclusion criteria were as follows: only school childrenwho were seven years of age; lack of comorbidities; only tra-ditional school backpacks (i.e., the children’s own backpackswhich they carried to school every day, designed to be carriedon both shoulders).

Exclusion criteria were as follows: children aged youngerthan seven or over eight years (e.g., children from thereception class and Year 2); lack of consent to participate inresearch;musculoskeletal, vision, and neurological disorders.

The parameters of body posture were determined usingthe Zebris Ultrasonic System with WinSpine 2.3 software.This system enables three-dimensional analysis of bodyposture. It consists of a sensorwith a stand, the basic CMS-HS

Figure 1: Subject’s position during the examination.

unit, and a single marker with a belt to be attached to the hipsof the subject. Tests using the ultrasonic spot indicator func-tion by identifying the anatomical landmarks on the subject’sskeleton, which are precisely displayed on a monitor con-nected to the computer [20–22]. Before the start of each test,the following anthropometric points weremarked on the skinof the subject: the spinous processes of the spine, the right andleft acromion, the right and left anterior superior iliac spine,the right and left iliac crest, the point of change of the thoracicspine into the lumbar spine, and the lower right and leftangle of scapula (Figure 1) [23]. The tests were performed bya physiotherapist with five years of experience as an operatorof the equipment and 15 years of experience in testing bodyposture.

The subject was positioned 80 cm from the receiver andequippedwith the transmitter belt.The position of the subjectwas habitual, with the upper limbs along the trunk and thelower limbs extended in the knee andhip joints.The followinginstructions were given: “stand in a comfortable manner”;“do not bend your knees”; and “look straight.” The childrenwere not instructed to straighten up. When the subject cor-rected their body posture, the measurement was repeated sothat functional defects were also noted [24, 25].

The following parameters of the subjects’ posture weremeasured: ThS (mm): total length of the spine; THL (mm):length of the thoracic spine; LS (mm): length of the lumbarspine; KKP (degrees): thoracic kyphosis angle, calculatedfrom the intersection of the tangents extending betweenthe spinous processes of Th1 and Th2 and Th11 and Th12(Figure 2); KKL (degrees): angle of lumbar lordosis, calcu-lated from the intersection of the tangents extending betweenthe spinous processes of L1 and L2 and L5 and S1 (Figure 2);TTI (degrees): total angle of anterior trunk inclination(Figure 3); and SCR (degrees): sacral angle in the study group(sacral angle is defined as the angle between the line connect-ing the spinous processes S1 and S3 and the frontal plane)(Figure 2).

BioMed Research International 3

Th1C7

Th12

L1

L5

S1

S3

Thoracickyphosis

Lumbarlordosis

Sacralangle(SCR)

Figure 2: Analysed parameters.

Th1C7

Th12

L1

L5

S1

S3

Total trunkinclination

Figure 3: Analysed parameters.

As a next step, the child’s body height, body weight, andschool backpack weight (along with its contents) were mea-sured. These measurements were made using the seca 213portable stadiometer height rod (digital scale with 0.1 kgaccuracy). The group was examined in the morning, duringschool hours, that is, during an ordinary school day accordingto the school timetable.

3. Statistical Analysis

The differences in posture between the groups (Group 1,weight of backpack less than 10% of child’s body weight, andGroup 2, backpack heavier than 10% of child’s body weight)were determined using the Mann-Whitney 𝑈 test, whichis equivalent to nonparametric variance. The correlationbetween the weight of the backpack carried by the child every

Table 2:The weight of the school backpacks carried by the subjects.

Mean Range SDWeight of school backpack (kg) 2.87 1.64–4.10 0.50Weight of school backpack inrelation to child’s body weight (%) 10.90 6.78–17.47 3.14

SD: standard deviation.

day and the parameters of posture in the sagittal plane wasinvestigated using Spearman’s correlation coefficient. Theresults were considered statistically significant at 𝑝 < 0.05.The obtained results were analysed statistically using STATIS-TICA 9.0.

4. Results

The number of children carrying school backpacks in accor-dance with recommendations (i.e., weighing less than 10% oftheir body weight) was 44 subjects (40.37%).

The weight analysis of the school backpacks and theirrelation to the body weight of the children showed thatthe weight of the carried load often exceeded the 10%recommended in the literature. Detailed results are shown inTable 2.

The parameters describing the spinal shapes of the twogroups (Group 1, with backpacks weighing less than 10%of the children’s body weight, and Group 2, with backpacksheavier than 10% of the children’s body weight) are shown inTable 3. The only statistically significant differences betweenthe groups were observed for the total length of the spine(𝑝 = 0.026).

A statistically significant relationship was revealedbetween the load of the school backpack and the total lengthof the spine, the length of the lumbar lordosis, the lumbarlordosis angle, and the angle of sacrum inclination. Withthe increase in the weight of the backpack, the measuredparameters decreased. No statistically significant differenceswere found for the following parameters: THL (length of thethoracic spine), KKP (angle of thoracic kyphosis), and TTI(total angle of anterior trunk inclination). Details are shownin Table 4.

5. Discussion

The issue of school backpack load is still a valid one [26, 27].The new conditions under which children begin to undertaketheir education may contribute to the emergence or worsen-ing of bad posture. Children’s spontaneous physical activity isrestricted during the mandatory school age. Their body pos-ture is influenced not only by the restricted room for move-ment but also by carrying external loads. Overloaded schoolbackpacks can be a threat to the correct development ofposture [28].

Children usually carry their backpacks for a rela-tively short period every day. Nevertheless, the relationshipbetween backpack load and spine shape in the sagittal planeobserved in the study arouses a certain interest. In our study,the school backpacks filled with books weighed on average


Table 3: Summary of the parameters characterizing the children’s body postures.

Backpacks lighter than 10% of body weight Backpacks heavier than 10% of body weight Mann-Whitney 𝑈 testMean Range SD Mean Range SD 𝑍 𝑝

ThS (mm) 375.4 350.3–400.5 25.1 357.0 320.7–393.3 36.3 2.223 0.026THL (mm) 230.4 212.5–248.3 17.9 223.4 203.7–243.1 19.7 1.252 0.211LS (mm) 107.0 90.6–123.4 16.4 98.4 77.7–119.1 20.7 1.454 0.146KKP (deg.) 47.4 33.8–61.0 13.6 43.8 31.1–56.5 12.7 1.414 0.157KKL (deg.) 26.6 12.3–40.9 14.3 23.9 12.2–35.6 11.7 1.112 0.266TTI (deg.) 4.2 2.3–6.1 1.9 3.4 1.4–5.4 2.0 1.345 0.179SCR (deg.) 24.5 14.7–34.3 9.8 19.5 9.3–29.7 10.2 1.927 0.054ThS (mm): total length of the spine.THL (mm): length of the thoracic spine.LS (mm): length of the lumbar spine.KKP (degrees): thoracic kyphosis angle, calculated from the intersection of the tangents extending between the spinous processes ofTh1 andTh2 andTh11 andTh12.KKL (degrees): angle of lumbar lordosis, calculated from the intersection of the tangents extending between the spinous processes of L1 and L2 and L5 and S1.TTI (degrees): total angle of anterior trunk inclination.SCR (degrees): sacral angle in the study group (sacral angle is defined as the angle between the line connecting the spinous processes S1 and S3 and the frontalplane).SD: standard deviation; 𝑍: Mann-Whitney 𝑈 test; 𝑝: significance level.

Table 4: The relationship between the child’s school backpack loadand the occurrence of changes in the parameters of the child’sbody posture in the sagittal plane, using Spearman’s correlationcoefficient.

Anthropometricparameters 𝑟

𝑠, 𝑝 (value) Interpretation

ThS −0.3999, (0.017)The heavier the backpack, thelower the total length of thespine

THL −0.2313, (0.181) Not significant

LS −0.3352, (0.049)The heavier the backpack, thelower the length of the lumbarlordosis

KKP −0.2695, (0.117) Not significant

KKL −0.5065, (0.002)The heavier the backpack, thesmaller the lumbar lordosisangle

TTI −0.0537, (0.759) Not significant

SCR −0.4279, (0.010) The heavier the backpack, thesmaller the sacral angle

ThS (mm): total length of the spine.THL (mm): length of the thoracic spine.LS (mm): length of the lumbar spine.KKP (degrees): thoracic kyphosis angle.KKL (degrees): lumbar lordosis angle.TTI (degrees): total angle of anterior trunk inclination.SCR (degrees): sacral angle.𝑟𝑠: Spearman’s correlation coefficient.

2.87 kg. The backpacks were weighed once during the study,assuming that the backpack weight would be similar everyday, based on the number of daily lessons; these data corre-spond with the findings of other researchers. Nevertheless,the issue should be taken into account when analysing theobtained results. It has already been mentioned that theresults are consistent with the results of other researchers, for

example, those of Al-Hazzaa regarding similarly aged chil-dren. In this study, the mean weight of the backpack was2.77 kg, but higher values were accepted for school backpackweight as a percentage of mean body weight (12.5%) com-pared to in our study (10.9%) [29]. In other parts of the world,higher values have also been recorded, such as 13.2% [30]and 12% [31]. Our study also confirmed this disturbing phe-nomenon: during the tests carried out in Year 1, the overloadof school backpacks was found among 60% of the respon-dents.

A study by Kułaga and Grajda found that a backpackweight exceeding 10–15% of the child’s body weight forcesthe child to compensate for the excessive load by tilting theirtorso forward. However, according to the authors, a greaterimpact on the children’s posture was produced by the wrongposition of the body, rather than the weight of the backpack[24]. Pau et al. found that an external load increased thedistribution of asymmetries in foot pressure forces on theground. In addition, carrying a school backpack in the wrongway was found to exacerbate existing disorders [32].

Relationships between a child’s school backpack loadand the total length of their spine, the size of their lumbarlordosis, and their sacrum inclination were all found inour study. When the school backpack weight was higher,greater decrease of the lumbar lordosis was observed, and thesacrum inclination was smaller. Such a situation may lead toa reduction in the natural curvature of the lumbar spine andrelated adverse consequences, such as reduced amortizationproperties of the spine, and asymmetric loading of interver-tebral discs, which can lead to overloading and degenerativechanges in the spine.

There was no relationship observed between backpackload and the length of the thoracic spine, the angle of thoracickyphosis, or the anterior inclination of the trunk. The lackof correlation with the angle of thoracic kyphosis in ourstudy may be due to the fact that over 40% of the children

BioMed Research International 5

wore backpacks according to the standard, that is, weighingless than 10% of the weight of the child. The habitual postureduring rest and learning should be controlled, and theweight of the school backpacks should also be checked byparents and representatives of the educational institutions.Continuous monitoring and systematic screening tests todetect abnormalities in body posture are also justified.

6. The Value of the Research

Studies evaluating the incidence of abnormal behaviour, suchas children wearing heavy backpacks and the relationshipbetween this and their posture, are important in the preven-tion of back pain. The observed reduction and shorteningof the lumbar spine as the weight of the carried backpackincreases may indicate a primary cause of subsequent futureoverloading and degenerative changes in the spine. It canalso help explain the occurrence of lower back pain inschool children, discussed widely in the literature [33–35].The unambiguous evidence showing that the weight of schoolbackpacks is related to the shape of spine curvature will allowschools to include compensation exercises in physical edu-cation curricula, ensuring optimum physical developmentby encouraging balanced and spontaneous physical activityduring the day (e.g., as recreation activities). Thus, opportu-nities to help protect the spine will be created.

7. Limitations of the Research

The weight of the backpacks without content (which wouldhave indicated the actual weight of the school books andnotebooks)was not examined, as theweightwas checked onlyonce. In addition, the study was not a longitudinal study con-ducted over a longer period, for example, at the beginning andthe end of the school year.

8. Conclusions

(i) Wearing a backpack heavier than 10% of one’s bodyweight can cause shallowing of the lumbar lordosisand a tendency towards a vertical position of thesacrum.

(ii) Monitoring the weight of children’s school back-packs by parents and teachers, as well as childrenthemselves, and enabling them to leave books andnotebooks at school would probably be beneficial inreducing the daily burden put on children’s spines.

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper.The study was fundedusing the authors’ own resources.

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